Michael A. Reale M.D. Ph.D., the candidate for a Clinical Investigator Award, is currently completing his Medical Oncology Fellowship and will continue on next year as a junior faculty member at the Yale School of Medicine. Further training to promote his development as an independent investigator will be conducted under the tutelage of Drs. Eric R. Fearon, Jon S. Morrow and Vincent T. Marchesi at the Boyer Center for Molecular Medicine of the Yale University School of Medicine. The Deleted in Colorectal Cancer (DCC) gene is a putative tumor suppressor that has been implicated in the development of several carcinomas, notably those of the colon, stomach, pancreas and breast. It encodes an approximately 155 kD transmembrane protein that bears significant similarity to the neural cell adhesion molecule family of proteins, a subfamily of the immunoglobulin superfamily. It is unique among tumor suppressor gene products in its presumed function as a cell adhesion molecule. The overall goal of this research is to further understanding of the role of a cell adhesion molecule in tumorigenesis. As there is an increasing appreciation of functional interactions between adhesion molecules and the cytoskeleton, and also a possible role for adhesion molecules in signal transduction, the specific focus of these studies will be the cytoplasmic domain of the DCC protein. Specific aim 1 proposes to identify and characterize cellular proteins that may interact with the cytoplasmic domain of the DCC protein. This aim will be approached in three ways -- co-immunoprecipitation assays, and the use of recombinant DCC cytoplasmic domain fusion proteins in "capture" assays and screening of cDNA expression libraries. Specific aim 2 proposes to characterize the DCC amino acid sequence involved in this protein interaction(s) by using a panel of truncated cytoplasmic domain fusion proteins in inhibition studies. Specific aim 3 proposes the construction of cytoplasmic domain mutant forms in eukaryotic expression vectors for transfection of mammalian cell lines. These will be utilized in the functional studies that constitute specific aim 4. Studies of function will examine DCC's demonstrated role in induction of neurite outgrowth and also attempt to demonstrate its presumed tumor suppressor ability. Though specific aim 1 forms the foundation of this proposal, it should be noted that aims 3 and 4 are not entirely dependent on the demonstration of cellular protein interactions with the DCC cytoplasmic domain.